This invention relates generally to a method and an apparatus for automatically applying solder to a printed circuit board having electrical parts mounted thereon, and more particularly to a method and an apparatus for transferring such printed circuit board for contact with molten solder in a container.
FIG. 1 of the accompanying drawings shows one of known transfer apparatus of this sort, in which a printed circuit board 2 with electrical parts 1 is detachably mounted on a carrier 3 which has its front and rear wheels 4 and 5 on a rail 6. The carrier 3 is driven by a conveyor chain, which is not shown, to run on and along the rail 6. The rail 6 is provided with a sunken portion, at which the lower side of the printed circuit board 2 is dipped in molten solder in a vessel 7 to solder the electrical parts 1 thereto while the carrier 3 travels from point F to G.
In this apparatus, in order to guide the printed circuit board 2 into the solder vessel, it is necessary to introduce the fore end of the printed circuit board 2 into the solder vessel while its rear portions are still going down the slope EF. Therefore, the sunken portion EH must have a large distance with a long slope of an easy grade between the points E and F and G and H. In addition, the solder vessel 7 is required to have a large length in the direction of travel of the carrier. As a result, there arise problems such as the increased size of the apparatus as a whole, the needs for a larger amount of molten solder and for a greater amount of heat for maintaining the solder in molten state.